چكيده فارسي :
نياز روز افزون به منابع آبي وانرژي پاك جوامع بشري را بر آن داشته تا با تحقيقات و مطالعات گسترده فناوري هاي قديمي را بهينه سازي كنند تا بيشترين بهره ممكن را از آنها ببرند. يكي از اين اختراعات سد ها هستند، سازه هايي كه بر روي رودها ايجاد مي شود. در گذشته ايجاد سدها عمومآ با هدف تامين آب آشاميدني و آبياري مزارع بوده اما امروزه نه تنها تامين كننده مصارف آبي است بلكه در ايجاد انرژي الكتريكي نيز مورد استفاده قرار مي گيرند. در بسياري از مطالعات، براي ارزيابي آسيب پذيري و ميزان صدمه ديدن سدها در هنگام وقوع زلزله از تحليل ديناميكي استفاده مي شود. عليرغم دقيق بودن اين روش، عدم قطعيت هاي فراواني در مراحل تحليل وجود دارد كه باعث هزينه بر بودن و طولاني شدن مطالعات مي شود. از اين رو محققان با بكار گيري روش تحليل استاتيكي غير خطي سرعت تحليل را بالا برده و هزينه ها را كاهش دادند. هدف تحقيق حاضر، بررسي عملكرد لرزه اي سدهاي بتني وزني با استفاده از تحليل استاتيكي غيرخطي (بار افزون) است. بدين منظور الگوهاي بار مورد استفاده در تحليل بار افرون در دو جهت بالادست و پايين دست به سازه سد اعمال مي گردد و مشاهدات نشان دهنده آن است كه به غير از الگوي بار مستطيلي تمامي الگوي هاي بار مورد استفاده در اين تحقيق بطور مناسبي مي توانند راستاي ترك را در بدنه سد به درستي تشخيص دهند.
چكيده لاتين :
A gravity dam is a dam constructed from concrete or stone masonry and designed to hold back water by primarily using the weight of the material alone to resist the horizontal pressure of water pushing against it. Gravity dams are designed so that each section of the dam is stable, independent of any other dam section. Gravity dams generally require stiff rock foundations of high bearing strength (slightly weathered to fresh); although they have been built on soil foundations in rare cases. The bearing strength of the foundation limits the allowable position of the resultant which influences the overall stability. Also, the stiff nature of the gravity dam structure is unforgiving to differential foundation settlement; which can induce cracking of the dam structure. Gravity dams provide some advantages over embankment dams. The main advantage being that they can tolerate minor over-topping flows as the concrete is resistant to scouring. Large over-topping flows are still a problem, as they can scour the foundations if not accounted for in the design. A disadvantage of gravity dams is that due to their large footprint, they are susceptible to uplift pressures which act as a de-stabilising force. Uplift pressures (buoyancy) can be reduced by internal and foundation drainage systems which reduces the pressures. During construction, the setting concrete produces a exothermic reaction. This heat expands the plastic concrete and can take up to several decades to cool. When cooling, the concrete is in a stiff state and is susceptible to cracking. The increasing need for clean water and energy resources for human societies has led them to optimize the old technologies with the best in research and studies to make the most of them. One of these inventions is dams, structures that are created on the rivers. In the past, the creation of dams was generally aimed at providing drinking water and irrigation of farms, but nowadays it is not only a source of water, but also electric energy. In many studies, dynamic analysis is used to assess the vulnerability and damage damages during an earthquake. Despite the precision of this method, there are many uncertainties in the analysis stages that make the study costly and prolonged. Therefore, using nonlinear static analysis method, researchers increased the speed of analysis and reduced costs. Pushover analysis is a simplified nonlinear analysis technique that can be used to estimate the dynamic demands imposed on a structure under earthquake excitations. It is a static-nonlinear analysis method where a structure is subjected to gravity loading and a monotonic displacement-controlled lateral load pattern which continuously increases through elastic and inelastic behavior until an ultimate condition is reached. Lateral load may represent the range of base shear induced by earthquake loading, and its configuration may be proportional to the distribution of mass along building height, mode shapes, or another practical means. The purpose of this study is to investigate the seismic performance of concrete gravity dams using nonlinear static analysis (pushover analysis). For this purpose, load patterns used in the pushover analysis are applied in both directions upstream and downstream of the dam structure. Observations show that, apart from the rectangular load pattern, all load patterns used in this research can adequately correlate Detect the crack in the dam body correctly.
